Replace IntoInitializer<T> with Into<PyClassInitializer<T>>

guide/src/class.md

@@ -189,12 +189,8 @@ created from Rust, but not from Python.
 For arguments, see the `Method arguments` section below.
 
 ### Return type
-Generally, `#[new]` method have to return `T: IntoInitializer<Self>` or
-`PyResult<T> where T: IntoInitializer<Self>`.
-
-If your `T: PyClass` inherits just `PyAny`, you can return just `Self` or `PyResult<Self>`.
-But if it inherits other `U: PyClass`, you have to return tuple `(T, U)` or
-`PyClassInitializer<T>`.
+Generally, `#[new]` method have to return `T: Into<PyClassInitializer<Self>>` or
+`PyResult<T> where T: Into<PyClassInitializer<Self>>`.
 
 For constructors that may fail, you should wrap the return type in a PyResult as well.
 Consult the table below to determine which type your constructor should return:
@@ -209,7 +205,7 @@ Consult the table below to determine which type your constructor should return:
 By default, `PyAny` is used as the base class. To override this default,
 use the `extends` parameter for `pyclass` with the full path to the base class.
 
-For convinience, `(T, U)` implements `IntoInitializer<T>` where `U` is the
+For convinience, `(T, U)` implements `Into<PyClassInitializer<T>>` where `U` is the
 baseclass of `T`.
 But for more deeply nested inheritance, you have to return `PyClassInitializer<T>`
 explicitly.
@@ -261,8 +257,7 @@ struct SubSubClass {
 impl SubSubClass {
    #[new]
    fn new() -> PyClassInitializer<Self> {
-       SubClass::new()
-           .into_initializer()
+       PyClassInitializer::from(SubClass::new())
            .add_subclass(SubSubClass{val3: 20})
    }
 

pyo3-derive-backend/src/pymethod.rs

@@ -174,7 +174,7 @@ pub fn impl_wrap_new(cls: &syn::Type, spec: &FnSpec<'_>) -> TokenStream {
 
             #body
 
-            match _result.and_then(|init| init.into_initializer().create_shell(_py)) {
+            match _result.and_then(|init| pyo3::PyClassInitializer::from(init).create_shell(_py)) {
                 Ok(slf) => slf as _,
                 Err(e) => e.restore_and_null(_py),
             }

src/derive_utils.rs

@@ -9,7 +9,7 @@ use crate::exceptions::TypeError;
 use crate::init_once;
 use crate::instance::PyNativeType;
 use crate::pyclass::PyClass;
-use crate::pyclass_init::IntoInitializer;
+use crate::pyclass_init::PyClassInitializer;
 use crate::types::{PyAny, PyDict, PyModule, PyTuple};
 use crate::{ffi, GILPool, IntoPy, PyObject, Python};
 use std::ptr;
@@ -184,17 +184,17 @@ impl<T: IntoPy<PyObject>> IntoPyResult<T> for PyResult<T> {
 
 /// Variant of IntoPyResult for the specific case of #[new]. In the case of returning (Sub, Base)
 /// from #[new], IntoPyResult can't apply because (Sub, Base) doesn't implement IntoPy<PyObject>.
-pub trait IntoPyNewResult<T: PyClass, I: IntoInitializer<T>> {
+pub trait IntoPyNewResult<T: PyClass, I: Into<PyClassInitializer<T>>> {
     fn into_pynew_result(self) -> PyResult<I>;
 }
 
-impl<T: PyClass, I: IntoInitializer<T>> IntoPyNewResult<T, I> for I {
+impl<T: PyClass, I: Into<PyClassInitializer<T>>> IntoPyNewResult<T, I> for I {
     fn into_pynew_result(self) -> PyResult<I> {
         Ok(self)
     }
 }
 
-impl<T: PyClass, I: IntoInitializer<T>> IntoPyNewResult<T, I> for PyResult<I> {
+impl<T: PyClass, I: Into<PyClassInitializer<T>>> IntoPyNewResult<T, I> for PyResult<I> {
     fn into_pynew_result(self) -> PyResult<I> {
         self
     }

src/instance.rs

@@ -4,7 +4,7 @@ use crate::gil;
 use crate::object::PyObject;
 use crate::objectprotocol::ObjectProtocol;
 use crate::pyclass::{PyClass, PyClassShell};
-use crate::pyclass_init::IntoInitializer;
+use crate::pyclass_init::PyClassInitializer;
 use crate::type_object::{PyObjectLayout, PyTypeInfo};
 use crate::types::PyAny;
 use crate::{ffi, IntoPy};
@@ -36,13 +36,13 @@ unsafe impl<T> Sync for Py<T> {}
 
 impl<T> Py<T> {
     /// Create new instance of T and move it under python management
-    pub fn new(py: Python, value: impl IntoInitializer<T>) -> PyResult<Py<T>>
+    pub fn new(py: Python, value: impl Into<PyClassInitializer<T>>) -> PyResult<Py<T>>
     where
         T: PyClass,
         <T::BaseType as PyTypeInfo>::ConcreteLayout:
             crate::type_object::PyObjectSizedLayout<T::BaseType>,
     {
-        let initializer = value.into_initializer();
+        let initializer = value.into();
         let obj = unsafe { initializer.create_shell(py)? };
         let ob = unsafe { Py::from_owned_ptr(obj as _) };
         Ok(ob)

src/lib.rs

@@ -128,7 +128,7 @@ pub use crate::instance::{AsPyRef, ManagedPyRef, Py, PyNativeType};
 pub use crate::object::PyObject;
 pub use crate::objectprotocol::ObjectProtocol;
 pub use crate::pyclass::{PyClass, PyClassShell};
-pub use crate::pyclass_init::{IntoInitializer, PyClassInitializer};
+pub use crate::pyclass_init::PyClassInitializer;
 pub use crate::python::{prepare_freethreaded_python, Python};
 pub use crate::type_object::{type_flags, PyTypeInfo};
 

src/prelude.rs

@@ -18,7 +18,7 @@ pub use crate::objectprotocol::ObjectProtocol;
 pub use crate::python::Python;
 pub use crate::{FromPy, FromPyObject, IntoPy, IntoPyPointer, PyTryFrom, PyTryInto, ToPyObject};
 // This is only part of the prelude because we need it for the pymodule function
-pub use crate::pyclass_init::{IntoInitializer, PyClassInitializer};
+pub use crate::pyclass_init::PyClassInitializer;
 pub use crate::types::PyModule;
 pub use pyo3cls::pymodule;
 pub use pyo3cls::{pyclass, pyfunction, pymethods, pyproto};

src/pyclass.rs

@@ -1,7 +1,7 @@
 //! An experiment module which has all codes related only to #[pyclass]
 use crate::class::methods::{PyMethodDefType, PyMethodsProtocol};
 use crate::conversion::{AsPyPointer, FromPyPointer, ToPyObject};
-use crate::pyclass_init::IntoInitializer;
+use crate::pyclass_init::PyClassInitializer;
 use crate::pyclass_slots::{PyClassDict, PyClassWeakRef};
 use crate::type_object::{type_flags, PyObjectLayout, PyObjectSizedLayout, PyTypeObject};
 use crate::types::PyAny;
@@ -130,26 +130,26 @@ pub struct PyClassShell<T: PyClass> {
 
 impl<T: PyClass> PyClassShell<T> {
     /// Make new `PyClassShell` on the Python heap and returns the reference of it.
-    pub fn new_ref(py: Python, value: impl IntoInitializer<T>) -> PyResult<&Self>
+    pub fn new_ref(py: Python, value: impl Into<PyClassInitializer<T>>) -> PyResult<&Self>
     where
         <T::BaseType as PyTypeInfo>::ConcreteLayout:
             crate::type_object::PyObjectSizedLayout<T::BaseType>,
     {
         unsafe {
-            let initializer = value.into_initializer();
+            let initializer = value.into();
             let self_ = initializer.create_shell(py)?;
             FromPyPointer::from_owned_ptr_or_err(py, self_ as _)
         }
     }
 
     /// Make new `PyClassShell` on the Python heap and returns the mutable reference of it.
-    pub fn new_mut(py: Python, value: impl IntoInitializer<T>) -> PyResult<&mut Self>
+    pub fn new_mut(py: Python, value: impl Into<PyClassInitializer<T>>) -> PyResult<&mut Self>
     where
         <T::BaseType as PyTypeInfo>::ConcreteLayout:
             crate::type_object::PyObjectSizedLayout<T::BaseType>,
     {
         unsafe {
-            let initializer = value.into_initializer();
+            let initializer = value.into();
             let self_ = initializer.create_shell(py)?;
             FromPyPointer::from_owned_ptr_or_err(py, self_ as _)
         }

src/pyclass_init.rs

@@ -109,34 +109,14 @@ where
     }
 }
 
-/// An extension of Into which extends the range of possible types from `#[pyclass]`'s `#[new]`.
-///
-/// In particular it permits for the return type of `#[new]` to be a (SubType, BaseType) pair
-/// which will also be initialized.
-///
-/// It is mainly used in our proc-macro code.
-pub trait IntoInitializer<T: PyClass> {
-    fn into_initializer(self) -> PyClassInitializer<T>;
-}
-
-impl<T, U> IntoInitializer<T> for U
-where
-    T: PyClass,
-    U: Into<PyClassInitializer<T>>,
-{
-    fn into_initializer(self) -> PyClassInitializer<T> {
-        self.into()
-    }
-}
-
-impl<S, B> IntoInitializer<S> for (S, B)
+impl<S, B> From<(S, B)> for PyClassInitializer<S>
 where
     S: PyClass + PyTypeInfo<BaseType = B>,
     B: PyClass + PyTypeInfo<Initializer = PyClassInitializer<B>>,
     B::BaseType: PyTypeInfo<Initializer = PyNativeTypeInitializer<B::BaseType>>,
 {
-    fn into_initializer(self) -> PyClassInitializer<S> {
-        let (sub, base_init) = self;
-        base_init.into_initializer().add_subclass(sub)
+    fn from(sub_and_base: (S, B)) -> PyClassInitializer<S> {
+        let (sub, base) = sub_and_base;
+        PyClassInitializer::from(base).add_subclass(sub)
     }
 }